1. Field of the Invention
This invention relates to a hydrostatic pressure XY table suitable for use in ultra-high precision machining, more particularly to a hydrostatic pressure XY table optimally suited for use, for example, in grinding the track surface of a magnetic head for a magnetic disk unit and the beveled surface contiguous with this track surface or in grinding a shaping die for plastic lenses.
2. Description of the Prior art
FIG. 1 of the attached drawings shows the configuration of a ferrite core 1 of a magnetic head. In the fabrication of a magnetic head employing such a ferrite core there is required a level of grinding precision and quality considerably higher than in general applications. This can be attriubuted to the following factors:
(1) The track width H determined by the two beveled surfaces contiguous with the track surface 2 is very small and must be machined with high dimensional precision and within very strict tolerance limits.
(2) The surface to be machined consists of a hard, brittle material like ferrite.
(3) The finished surface must be of high quality.
This type of machining work is generally carried out by grinding or lapping. Because of the brittle nature of the material that has to be machined, however, even the slightest vibration of the grinder etc. used for the operation is liable to cause chipping of the machined surface and it is thus necessary to assure high precision rotation of the grinding tool and to feed the work with utmost smoothness free from the influence of any irregularities on the guide surfaces.
In the ordinary XY table there are used sliding or rolling guide surfaces. The first of these is susceptible to sticking and slipping during low-velocity feeding while the latter tends to give rise to minute table vibration during travel of the rollers. Moreover, the nut which engages with the lead screw in the conventional XY table has either an acme or bore screw thread. These are also disadvantageous since the acme screw thread has a friction problem and the bore screw thread has poor damping capacity and a tendency to generate minute vibration. As a result, with the XY tables used up to now chipping of the material being machined and other defects have been common.